This invention relates generally to assessment and monitoring of structures and more specifically, to methods and systems for using active surface coverings for structural assessment and monitoring.
Composite materials are increasingly utilized in a wide variety of applications, including for aircraft structures. Multi-functional systems using composite material having complex geometries, however, can be a maintenance burden for servicing personnel. In addition, the maintenance tools, procedures, and practices for metallic aircraft structures generally are not compatible or cost effective with composite aircraft structures. Composite aircraft structures include mixtures of bonded and bolted laminates with a variety of metallic and composite substructures. Other examples include composite sandwiched structures and other adhesive bonded panels including assemblies and structures with contoured surfaces. It is desirable to inspect such structures to identify any defects, such as cracks, discontinuities, voids, or porosity, which could adversely affect the performance of the structure.
With respect to inspecting aircraft structure, in-service structural health monitoring (SHM) sensors are often part of a permanently installed system that includes other electronic hardware. Such other hardware takes up space, is heavy, and is typically mounted and wired into position on an aircraft. Known SHM sensors typically also require energization from a power source during operation. Space, weight, and power consumption factors are continually examined for reduction in aircraft design and configuration.
Non-destructive evaluation (NDE) sensors are generally placed by hand onto a structure under inspection by an inspector. Such inspectors typically do not have easy access to all the locations, for example, on an airframe, that might require inspection. Often, at least a portion of such structures has to be removed in order to inspect it, or secondary structures adjacent to the structure to be inspected. In addition to the time consuming and labor intensive aspect of NDE, there is also a danger of damaging an aircraft component or structure in connection with such NDE. NDE may be performed during personnel training sessions, field testing of the composite product, or after the completed structure has been put into service to validate integrity and fitness of the structure. NDE is sometimes referred to as non-destructive inspection (NDI).
Utilization of composite structures and a continuing shift towards lightweight composite and bonded materials, dictate that devices and processes are made available to ensure structural integrity, production quality, and lifecycle support. However, known non-destructive evaluation and non-destructive inspection methods still utilize sensors that are temporarily placed on to the exterior surface or an interior surface of a structure in order to accomplish the inspection. The time and labor costs associated with placement of these sensors is not insignificant. In addition, temporary placement of sensors and sensor grids may result in incorrect placement for the tests that are to be performed.